Current Differential Relay
WILMAR™ Protective Relays – WCD Series
Function:
87
•
ANSI/IEEE C37.90-1978
TERMINAL STRIPS
#6 - 32 SCREWS
Current Differential Relays are used for the protec-
tion of transformers, motors and generators, by
comparing the magnitude of the current entering
and leaving the protected circuit. On a given phase
winding, any difference between the two currents
will indicate an internal fault; the relay will sense the
vectorial difference between the two currents of the
protected section and will initiate a quick disconnec-
tion of the unit, to prevent disastrous consequences.
The relay may also be used to protect internal faults
on transformers, such as: ground faults, shorted
winding, leakage between primary and secondary,
etc. It will sense and compare primary vs. secondary
currents, once the turns ratio has been taken into
consideration.
3
4
3
7
/
8
4
1
/
2
Note:
Dimensions in inches. Multiply values by 25.4 for dimensions in mm.
4
7
/
8
4
5
/
8
Operation:
With control voltage applied, the output contacts
(shown in the de-energized position) will remain de-
energized as long as the difference between the two
input currents remains below the preset trip value.
The contact will transfer to the engerized position
when the current difference exceeds the trip value.
PART NUMBER SELECTION
.172 DIA.
4 MTG. HOLES
PART NUMBER SELECTION
PRODUCT SPECIFICATIONS
Sample Part No.
WCD-230AC-1-A
Type:
WCD - Close Differential
Control Voltage VAC & VDC
120AC
25DC
208AC
48DC
230AC
125DC
380AC
416AC
460AC
525AC
575AC
Trip Adjustment Range
.5 = 0.1 amp to 0.5 amp
1 = 0.2 amp to 1.0 amp
2 = 0.4 amp to 2.0 amp
Options
A = Two normally open contacts
B = Two normally closed contacts
H = Contacts rated 3 amp at 125 VDC
P = Transient protection is provided in compliance
with ANSI/IEEE C37.90-1978
Consult factory for additional models.
Part Number
WCD Series
Line Current ..................................... Single Phase, AC current, 50-400 Hz Direct or from CT
5 amp continuously
20 amp 30 seconds
200 amp, 0.10 seconds
Control Voltage ................................ See Part Number Selection
Differential Trip Point ....................... Screwdriver adjustable. See Part Number Selection
Operating Temperature .................... -40
o
C to +75
o
C
Burden .............................................. Current input: 2.5 VA max.
Control voltage DC: 2 W max.
AC: 2 VA max.
Output Contacts ............................... One set, N.O., One set N..C.
Contact Ratings ................................ 5 amp resistive at 120 VAC or 28 VDC
Notes:
1. Remove black screws for access to the trip adjustments.
2. Clockwise rotation of the adjustment potentiometer will raise the current differential trip point.
3. The output contacts are shown de-energized.
Tyco Electronics
/ www.tycoelectronics.com / Factory Direct Technical Support: 800-253-4560, ext. 2023 (U.S., Canada, Mexico) or 805-220-2020, ext. 2023 (International)
35
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